US 3632378 A
Tandem coating of paper web on one side with a clay coat and on the other side with a coating of pressure-rupturable encapsulated materials with the clay coat applied first and with a calender immediately before the coating with the encapsulated materials.
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Description (OCR text may contain errors)
United States Patent Inventor Thomas W. Busch Appleton, Wis.
Appl. No. 795,663
Filed Jan. 31, 1969 Patented Jan. 4, 1972 Assignee Appleton Papers, Inc.
The portion of the term of the patent subsequent to Oct. 27, 1987, has been disclaimed.
METHOD AND APPARATUS FOR MANUFACTURE OF DUAL COATED SHEET WITH PRESSURE RUPTURABLE MATERIALS 2 Claims, 2 Drawing Figs.
US. Cl 117/36.2, 117/64,117/68,117/119.8,117/156 Int. Cl 841m 5/22 Field ofSearch 117/36.2,
Primary Examiner-Murray Katz AttorneyMeDougall, Hersh, Scott & Ladd ABSTRACT: Tandem coating of paper web on one side with a clay coat and on the other side with a coating of pressure-rupturable encapsulated materials with the clay coat applied first and with a calender immediately before the coating with the encapsulated materials.
METHOD AND APPARATUS FOR MANUFACTURE OF DUAL COATED SHEET WITH PRESSURE RUPTURABLE MATERIALS This invention relates to the art of coated papers, and it relates more particularly to the method and apparatus for the fabrication of a two side coated manifold sheet in which at least one of the coatings is formulated with a pressure-sensitive material of the type described in the patents hereinafter set forth.
This invention has application to the manufacture of a manifold sheet adapted for use as an intermediate sheet in a manifold assembly and in which the manifold sheet is sometimes referred to as a colorless carbon. It will be understood that the concepts of this invention will have application also to the manufacture of other two side coated paper products in which one or both of the coatings contain materials which are pressure-sensitive such as a coating containing pressure rupturable capsules.
in the U.S. Pat. Nos. 2,299,693; 2,374,862; 2,548,366; 2,712,507; 2,730,456; 2,730,457; 2,800,457; 2,929,736; 2,293,582; 3,020,171; 3,104,980; and 3,129,103, description is made of a copy process and materials for use in the practice of same in which separate coatings are provided on suitable carrier sheets in which one of the coatings is formulated to contain a liquid reactant such as a colorless dye component dissolved in a liquid solvent and which is encapsulated in microscopic capsules uniformly distributed throughout the coating (hereinafter referred to as the emulsion coat), while the other coating is formulated of clay or other particulate substance which is adapted to react with the liquid in response to release from the capsules to form a colored image (hereinafter referred to as the clay coat). When the coating containing the encapsulated liquid is positioned in surface contact with the clay coating, no color develops until pressure is applied by pen, pencil, stylus, typewriter key, die impression or the like, or by heat to rupture the capsules in the imaged areas whereby the liquid released from the ruptured capsule wets out the adjacent receptive material in the clay coating to develop the image.
In a manifold assembly, the top sheet in the assembly will be fabricated with only its underside coated with the emulsion coat, while the bottom sheet in the assembly will be coated on its top side with only the clay coating. All of the sheets in between will be coated on the underside with the emulsion coat and on the top side with the clay coat in a two side coated sheet.
Since the emulsion coat comprises the more expensive materials and therefore represents the more expensive coating, it is desirable to fabricate the clay coat with a high degree of surface smoothness so as to be able to make more effective contact with the emulsion coat and maximize the utilization of the encapsulated liquid released from the coating. in the light of the fact that the emulsion coat is sensitive to pressure which might rupture the capsules, it has been the practice to coat the paper first with the clay coat whereby the latter can be calendered to smooth the coating before application of the emulsion coat.
It is an object of this invention to produce and to provide a method and means for producing a two side coated paper of the type described in which the coatings are sufficiently smooth and uniform throughout the surface of the sheet and wherein the coated sheet is relatively free of curl or roll so as to lie flat while processing and in the manifold assembly.
More specifically, it is an object of this invention to provide a method and means for the manufacture of two side coated paper in which at least one side is coated with a composition containing pressure-sensitive capsules; in which the dual coating can be carried out in a single continuous multiple coating process; in which the dual coated paper is relatively free of roll or curl, and in which the process can be carried out in a simple and efficient manner, with a minimum amount of time, labor, and equipment.
These and other objects and advantages of this invention will hereinafter appear, and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawing, in which FIG. 1 is a schematic elevational view of a coating machine embodying the features of this invention, and
FIG. 2 is an enlarged perspective view, partially in section, of a dual coated manifold sheet produced in accordance with the practice of this invention.
Although the invention is addressed to the method and apparatus for the dual coating of paper base stock, the problem sought to be overcome by this invention arises primarily by reason of the unique characteristics of the compositions with which the base paper is coated and to combine in a single low cost process what has previously been a two or three step highcost process Briefly described, the emulsion coating is formulated of an aqueous composition containing rupturable microscopic capsules of tanned gelatin containing a liquid color-forming ingredient, such as a colorless dyestuff dissolved in an organic solvent. There may be included within the emulsion coating composition, a substantial amount (up to 50 percent by weight of the capsules) of a coarse, solid particulate material, such as cellulose fibers suspended with the rupturable capsules and in which a small amount of water-soluble binder may be dissolved in the aqueous medium. For a more detailed description of the emulsion coating, reference may be made to the examples in U.S. Pat. No. 2,71 1,375, and others of the patents heretofore set forth.
The clay coating comprises an aqueous system having clay, such as attapulgite clay or special kaolin clays, in finely divided form, suspended therein, with or without other fillers such as calcium carbonate, silica gel, satin white and the like, and a small amount of resinous binder. For a more detailed description and formulation of the clay coating composition, reference may be made to the examples in the aforementioned patents.
Referring now to the concepts of the invention in a method and apparatus for the manufacture of intermediate sheets having dual coatings of the type described on opposite sides of the paper base sheet, the paper raw stock, such as l3-pound manifolding bond, is supplied in the form of rolls 10 mounted for free rotational movement on a spindle 12 supported on the unwind stand 14. The web 16 of raw stock paper is passed from the roll 10 over a series of idler rollers and guide rollers 18 to a first coating station 20.
The first coating station comprises an applicator roll 22 in contact peripherally first with a pickup roll 24 and then with a metering roll 26. The lower portion of the pickup roll 24 dips into the bath of the clay coating composition to pickup a layer of clay coating, a portion of which transfers to form a layer on the peripheral surface of the applicator roll 22. Before the applicator roll 22 engages the underside of the paper web 16, it is engaged peripherally by the metering roll 26 which is effective to smooth the layer of clay coating and to meter the layer before contact for transfer to the paper. The described means for transfer of a smoothly metered coating to the one side of the paper web is referred to as the three roll transfer" and is more fully described in my copending application Ser. No. 555,154, filed June 3, l966, and entitled Web Coating System and Method." The applicator roll 22 engages the bottom side of the paper web 16 as it passes between guide rolls 30 and 32 and a metered quantity of aqueous clay coating composition is applied to the bottom side of the paper web. An amount corresponding to about 3-6 pounds per 3,000 square feet of surface area is applied.
From the first coating station 20, the one side coated web is advanced directly to an air knife 34 which cooperates with the turning roll 36 to meter the coating on the surface of the paper and uniformly to distribute the coating composition over the surface thereof. The coated web is advanced, while wet with the clay coating composition, from the air knife through one section 42 of a drying oven maintained at a temperature of about 220 to 300 F. while supported on an endless belt 44. The upper run of the belt is supported on rollers 46 arranged in a substantially arcuate path through the dryer and, for this purpose, it is preferred to make use of a foraminous belt or a belt formed of a vapor permeable material to enable the escape of water vapor therethrough when released from the coating. The endless belt 44 turns about rollers 48 and 50 outside the dryer and the return run passes through the dryer section to maintain temperature while being supported on a bottom run of rollers 52 provided with a takeup roller 54 for maintaining the proper tension in the supporting belt. For a more detailed description of the drying system, reference can be made to my US. Pat. No. 3,311,499
Before application of the emulsion coating of encapsulated materials, the one side clay coated paper web is advanced in rapid sequence through an in-line calendar, illustrated in the drawing as a five-roll calender 61 with hard steel rolls. The calender step is effective to improve smoothness, improve resistance to distortion on wetting, and reduce porosity of the paper whereby a desirable capsule coating can be formed with the application of less of the more expensive capsule coating composition. This not only gives a considerable savings in cost, but wet-out occurs more as a surface phenomenon instead of penetration, with the result that higher speeds can be obtained with less curl or cockle in the dual coated manifold sheet.
Returning now to the drawing, the clay coated paper l6, with the dried clay coating 60 on the top side thereof, is passed through the calender 61 and then over a series of guide rolls and tensioning rolls 62 to a second coating station 64 where application is made of the aqueous coating composition of the encapsulated materials, hereinafter referred to as the emulsion coating. This second coating station is of the same construction as the first in that it comprises an applicator roll 66 in contact with the uncoated side of the paper web 16, a metering roll 72 and a pickup roll 74, having its lower portion inserted in a bath of the emulsion coating composition in pan 76. The coating composition transfers from the periphery of the pickup roll to the periphery of the applicator roll, and the amount applied by the applicator roll is metered by the metering roll of the described three-roll transfer. Application is made while the web is supported between the guide rollers 68 and 70. The composition is applied in coating weights of about 3-4 pounds per 3,000 square feet of surface area.
From the coating station 64, the coated web is advanced to a second air knife 78 and over roller 80 which again operates to meter the amount of coating composition allowed to remain on the web and to distribute the coating uniformly across the web. Following the air knife, the clay coated surface is engaged by one or more reversing smoothing rolls 82 to smooth the coating by the reverse rolling technique. While such reversing rolls are preferred for improving the smoothness of the coating, they are not essential for the emulsion coat.
From the smoothing rolls 82, the web coated on both sides and turned about the roller 80 to position the dried clay coat lowermost with the wet emulsion coat uppermost, is advanced over a suction apron 84 and then to an upper section 86 of the drying oven through which it is carried on the surface of a supporting endless belt 88. The upper run of the belt is supported on longitudinally spaced-apart crosswise extending rollers 90 arranged in an arcuate path through the dryer and the belt continues to support the web for a short distance beyond the exit of the dryer whereafter the belt turns downwardly and back about rollers for return through the oven. A takeup roller 92 is provided outside of the dryer for adjusting the tension of the belt. As with the belt 44, it is preferred to make use of a vapor-permeable belt to enable the escape of vapors therethrough during passage through the dryer.
The web 16 coated on one side with a dried emulsion coat 6|) and on the opposite side with a dried clay coat 94 is passed over a series of guide rollers and tensioning rollers 96 to a windup roll 98 mounted on a winder stand 100 and powered to wind the coated web onto the roll. Thus the web is drawn through the coating apparatus and dryer under tension supplied by the windup roll.
While in prior processes, the coatings have been applied in the same order by first applying the clay coat and then the emulsion coat, such coatings have been applied in separate operations on separate machines with a separate calender on a still other machine in between. Such three-unit process requires considerably more capital investment, space, and manpower, and the nonintegrated arrangement leads to problems of transportation and scheduling which interfere with the fast economical production of the manifold sheet.
Efforts have been made to combine the operation into a single one on the machine coating operations by first applying the emulsion coat and then the clay coat with the possible eiimination of the calender, but certain advantages from the standpoint of quality and performance are achieved when the order is reversed and in-line calendering is employed im mediately in advance of emulsion coating.
From the standpoint of economy, the capsule emulsion coating represents the more expensive coating. Thus, in use, it is desirable to have optimum surface smoothness in the clay coat for optimum contact between the emulsion coat and clay coat in the copy system, thereby to optimize the utilization of the encapsulated liquid upon release from the capsules.
Further, from the standpoint of economy, it has been found that when the clay coated paper web is calendered in the manner described immediately prior to wetting the paper with the aqueous emulsion coating, the amount of emulsion coating applied to the paper can be reduced and thereby further to reduce cost and weight without loss of performance.
From the standpoint of performance, it has been found that the improved smoothness and reduced porosity is retained even when the coated sheet is rewet with the aqueous emulsion coating in that less penetration of the aqueous emulsion coating occurs into the base paper. As a result, less moisture is required to be driven out of the paper whereby higher speeds can be achieved in manufacture with less wrinkle or cockle in the dried sheet.
lt will be apparent that the invention which combines the tandem coating, three-roll metering and high-speed drying in a continuous operation on a single machine places less demand on previous or subsequent processing equipment, improves quality, markedly reduces cost of operation, greatly improves raw material utilization, as well as to produce a better and more uniform product.
The tandem process described produces the described dual coated paper of better quality, better copy quality, improved resistance to smudge due to smoothness of the clay coating, improved character definition because of the elimination of coating pattern, minimum to no curl or cockle, less paper distortion-all at a lower material cost with less waste.
It will be further understood that numerous changes may be made in the details of formulation and operation, without departing from the spirit of the invention, especially as defined in the following claims.
1. In the method for high speed production of a capsule coated carbonless paper having a uniform pressure-sensitive capsular coating on one side and an image receiving clay coating on the opposite side, the steps, in the sequence set forth, of metering an aqueous clay coating composition onto one side of an endless sheet of relatively nonabsorbent bond paper, advancing the clay coated sheet continuously through a drying zone for removal of moisture from the clay coating composition, calendering the clay coated sheet to smooth the coating and densify the paper, metering an aqueous emulsion coating of pressure rupturable capsules onto one side of the sheet opposite the clay coating as a continuous operation immediately following the calendering step, and advancing the dual coated sheet continuously through a drying section while the sheet is supported, with the emulsion coated side uppermost, on a supporting surface traveling at about the same linear speed as the paper for removal of moisture by directing hot air jets onto the coated side of the sheet while the sheet is supported in a relaxed state.
2. The method as claimed in claim 1 in which, while the clay coated sheet is continuously advanced through the drying zone, the sheet is supported with the clay coated side upper-